Embodiments of the present invention generally relate to optical transmission systems. In particular, embodiments of the present invention relate to an apparatus for forming a wavelength division multiplexed (WDM) signal having orthogonally polarized optical channels of a fiber-optic transmission system.
Modern fiber-optic transmission systems use wavelength division multiplexed (WDM) techniques to transmit a plurality of optical channels via a single-mode optical fiber. However, non-linear transmission effects in optical fibers may cause interactions between adjacent optical channels that limit performance of such systems.
In WDM systems, cross-channel interference may be reduced by using pair-wise orthogonally polarized optical channels, as described in commonly assigned U.S. Pat. No. 6,134,033, issued Oct. 17, 2000; and U.S. Pat. No. 6,459,515 B1, issued Oct. 1, 2002, the entire disclosures of which are incorporated herein by reference. These systems use polarization-maintaining components, as well as polarization-maintaining fibers. Presently, such components and fibers are expensive and some (e.g., polarization-maintaining dispersion compensating fibers) may not be readily available.
Therefore, there is a need in the art for an improved apparatus for forming a WDM signal having orthogonally polarized optical channels of a fiber-optic transmission system.